The invention concerns a phonograph turntable control system, provided with means for lifting and lowering the tone arm, means for swinging the tone arm horizontally, means for detecting when the tone arm has been lowered onto a record and when the tone arm has reached the end of a record, and provided with touch-activated switches or touch buttons activated by the user, with settable and resettable electrical or electronic storage devices which register commands for the swinging, lifting and lowering of the tone arm and for turning on and off the drive motor for the platter.
In conventional phonographs, the control functions for the platter motor and the tone arm are implemented using predominantly mechanical means. Use is typically made of transmissions, gearing, levers, and the like. However, mechanical components such as these wear and age quite rapidly and are very susceptible to malfunction.
For certain special functions, it has already been proposed to make use of nonmechanical control devices which make for a considerable improvement in overall phonograph turntable construction. For example, German patent DT-PS No. 1,243,412 discloses a shutoff system for the platter drive motor of a phonograph turntable. The tone arm has connected to it a light shield which, when the tone arm swings, moves through the light path of a photoelectric detector. The speed of swinging movement of the tone arm is sensed, and when a certain speed of swinging movement is reached, the platter drive motor is shut off by means of a transistor-controlled switching relay. An RC-circuit receives the output signal of the photodetector and produces a voltage whose magnitude is dependent upon the rate of change of the light-dependent current produced by the photodetector.
German published patent application DT-OS No. 1,810,983 discloses another photoelectric switching system for phonograph turntables. The photoelectric switching system includes a stationary light source and a stationary light detector. A deflecting mirror is mechanically coupled to the tone arm and moves as the tone arm becomes inwardly displaced during tracking of the spiral record groove. The deflecting mirror is preferably oriented perpendicular to a radial plane which passes through the swinging axis of the tone arm. When the tone arm reaches a position calling for the initiation of a switching operation, the deflecting mirror directs the light from the light source onto the light detector.
Other automatic switching devices are known in the art, for switching off a phonograph at the end of a record, for lowering the tone arm and for controlling the tone-arm drive mechanism, for example in German published patent applications DT-OS No. 19 57 562, DT-OS No. 20 54 880, DT-OS No. 20 11 005 and DT-OS No. 19 54 673, and also in German allowed patent application DT-AS No. 19 17 241. However, these various automatic switching systems relate to various individual aspects of electronic phonographic control.
The Audiodynamics Corporation (ADC Accutrac 4000, brochure AVO 17608) produces an automatic phonograph turntable in which various functions can be triggered by pushbutton action or by wireless remote control. However, this known system is not provided with sensor operator control elements.
Finally, German published patent application DT-OS No. 21 04 692 discloses a system in which the various functions to be performed for turntable control are made to have a much more automatic character, and are implemented using electronic means. The tone arm is moved by two electromechanical positioning devices, one for horizontal swinging of the tone arm, the other for vertical lifting and lowering of the tone arm. Use is made of two electrical storage devices for storage of swing-in and swing-out information. The tone arm is lifted as soon as one of the storage devices registers a signal. Swinging of the tone arm is not possible until after the lifting movement of the tone arm has been completed. The storage devices are erased when tone-arm-position transducers signal the end of the operation involved. The use of settable storage devices makes it possible to dispense with the use of electrical switches of the type which must be held locked in activated position by mechanical locking means; instead, use can be made of touch-activated switches, very-low-force touch buttons, and the like.
The present invention proceeds from the state of the prior art last referred to.